Non-patent Literature 1 describes a typical related art of DNS name resolution system.
The DNS name resolution system of Non-patent Literature 1 includes a user program, a resolver, and a name server.
The DNS name resolution system of Non-patent Literature 1 with a structure as described above operates as follows.
The user program communicates to the resolver as a user query DNS name information indicating the DNS name (e.g. domain name) that the client needs to resolve. The resolver generates a DNS query packet containing the DNS name information, and transmits the generated DNS query packet to the name server.
The name server actually performs the DNS name resolution process, generates a DNS response packet that contains the resolution information indicating the resolution result (e.g. the IP address corresponding to the domain name), and transmits the generated DNS response packet to the resolver. The user program receives the resolution information as a user response from the resolver.
Non-patent Literature 2 describes the concept of a typical DNS name resolution system and examples of character strings that can be used as DNS name information.
Non-patent Literature 3 gives a definition of an URL (Uniform Resource Locator).
Non-patent Literature 1: RFC1035 “DOMAIN NAMES—IMPLEMENTATION AND SPECIFICATION”, November 1987, [search made on Feb. 19, 2009], Web URL: http://www.ietforg/rfc/rfc1035.txt.
Non-patent Literature 2: RFC1034 “DOMAIN NAMES—CONCEPTS AND FACILITIES”, November 1987, [search made on Feb. 19, 2009], Web URL: http://www.ietf.org/rfc/rfc1034.txt.
Non-patent Literature 3: RFC1738 “Uniform Resource Locators (URL)”, December 1994, [search made on Feb. 19, 2009], Web URL: http://www.ietf.org/rfc/rfc1738.txt.
A typical service provision method is in a form in which a server responsible for providing services has a finite number of fixed IP addresses (one, in many cases). The server provides a plurality of services through the finite number of fixed IP addresses.
In this method, after, through the DNS name resolution process, acquiring the IP address of the server responsible for providing services, the client is further required to designate the information to identify the service to which the client wants to connect to from within a plurality of the services provided by the server to reach the actual service. In other words, the client is unable to reach the actual service through the DNS name resolution process alone.
Another service provision method, which is rather special in kind, is in a form in which a server responsible for providing services has a large number of unfixed IP addresses. The server assigns a dedicated IP address to each service and provides a service through the IP address assigned thereto. In this method, after acquiring the information of IP address, the client can find the service to which it wants to connect to. In other words, the client is able to reach the actual service through the DNS name resolution process alone.
Therefore, anticipating the increasing popularity of the latter form of providing services, it would be necessary to build a DNS name resolution system that allows the client to reach the actual service through the DNS name resolution process alone.
The art described in Non-patent Literature 1 has several problems in building a DNS name resolution system as described above.
The first problem is that DNS name information that can be included in a DNS query packet is restricted to name information that is fixed in nature (e.g. the domain name of a server node). Besides name information, additional information that may change dynamically (e.g. information concerning a service) cannot be used as part of a query.
The reason for this is that the DNS name resolution system itself has inherently been designed and implemented for the purpose of providing name information that is fixed in nature (e.g. IP addresses) as resolution information.
The second problem is that, even if additional information that may change dynamically is used as DNS name information to be included in a DNS query packet, there is no function to analyze the DNS name information.
The reason for this is that the DNS server itself does not inherently have any function to analyze DNS name information containing additional information that is dynamic in nature.
The third problem is that it is restricted to Web applications among communication applications that can use additional information that may change dynamically, as DNS name information to be included in a DNS query packet, because Web applications can designate additional information in the form of URL by use of the Hyper Text Transfer Protocol (HTTP).
The reason for this is that every communication application is provided with a function to resolve DNS names but not a function to interpret URLs. Only Web applications have the latter function.
An object of the invention is to provide a DNS name resolution system, an override agent, and a DNS name resolution method, which enable every communication application on a client node to use additional information that may change dynamically, besides name information that is fixed in nature, as DNS name information to be included in a DNS query packet.